Method for manufacturing pixel structure

ABSTRACT

A method for manufacturing a pixel structure is provided. A first conductive layer is formed on a substrate and patterned using a first mask to form a gate. A dielectric layer is formed over the substrate to cover the gate. A semiconductor material layer and a second conductive layer are sequentially formed over the dielectric layer. The second conductive layer is patterned using a second mask to form a pixel electrode. A patterned photo-resist layer is formed by using the first mask again such that the semiconductor material layer above the gate is protected. The semiconductor material layer is patterned to form a semiconductor layer using the pixel electrode and the patterned photo-resist layer as an etching mask. The patterned photo-resist layer is removed. A third conductive layer is formed and patterned to form a source/drain by using a third mask. The drain is electrically connected to the pixel electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 94147530, filed on Dec. 30, 2005. All disclosure of theTaiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a pixelstructure, and more particularly to a method for manufacturing a pixelstructure with relatively fewer number of masks.

2. Description of Related Art

With the process of modern information technology, various types ofdisplays have been widely in consumer electronic products such as cellphones, notebook computers, digital cameras, and personal digitalassistants (PDAs). Among these displays, the liquid crystal display(LCD) and the organic electroluminescence display (OELD) have become themainstream on the market due to their advantages of being light, small,and low in power-consumption. The manufacturing processes for both theLCD and the OELD include forming a pixel structure array over asubstrate through a semiconductive process.

FIGS. 1A to 1G depict a cross-sectional flow chart of manufacturing aconventional pixel structure. First, referring to FIG. 1A, a gate 20 isformed on a substrate 10 by using a first mask (not shown). Referring toFIG. 1B, a first dielectric layer 30 is formed over the substrate 10 tocover the gate 20. Referring to FIG. 1C, a channel layer 40 is formed onthe first dielectric layer 30 by using a second mask (not shown).Referring to FIG. 1D, a source 50 and a drain 60 are subsequently formedon the channel layer 40 by using a third mask (not shown). Referring toFIG. 1E, a second dielectric layer 70 is formed over the substrate 10 tocover the channel layer 40, the source 50 and the drain 60. Referring toFIG. 1F, a contact hole H is formed in the second dielectric layer 70 byusing a forth mask (not shown). Referring to FIG. 1G, a pixel electrode80 is then formed on the second dielectric layer 70 by using a fifthmask (not shown). The pixel electrode 80 is partly filled in the contacthole H and is electrically connected to the drain 60. Thus, thefabrication of the pixel structure 90 complete.

As described above, the above pixel structure 90 five-mask processes andmany process steps are required, and the fabrication time is relativelylong. Because of many process steps, defects may occur in the pixelstructure 90, and also the fabrication yield may be substantiallydecreased and the overall fabrication cost may be substantiallyincreased.

SUMMARY OF THE INVENTION

In view of this; an object of the present invention is to provide amethod for manufacturing a pixel structure using comparatively fewermask process steps.

Another object of the present invention is to provide a method formanufacturing a pixel structure, wherein the number of mask processsteps is comparatively reduced.

In order to achieve the aforementioned or other objects, the presentinvention provides a method for manufacturing a pixel structure. Themethod for manufacturing the pixel structure includes the followingsteps. First, a first conductive layer is formed on a substrate. Thefirst conductive layer is patterned to form a gate by using a firstmask. Next, a dielectric layer is formed over the substrate to cover thegate. A semiconductor material layer and a second conductive layer aresequentially formed over the dielectric layer. Next, the secondconductive layer is patterned to form a pixel electrode by using asecond mask. A patterned photo-resist layer is formed over the substrateby using the first mask again for protecting the semiconductor materiallayer above the gate. Next, the semiconductor material layer ispatterned to form a semiconductor layer by using the pixel electrode andthe patterned photo-resist layer as masks. Then, a third conductivelayer is formed over the substrate. The third conductive layer ispatterned to form a source/drain by using a third mask. The drain iselectrically connected to the pixel electrode.

According to one embodiment of the present invention the step of formingthe semiconductor layer further includes patterning the dielectric layerby using the pixel electrode and the patterned photo-resist layer asmask to expose a portion of the substrate.

According to one embodiment of the present invention, the step offorming the pixel electrode further includes forming a contact hole toexpose a portion of the semiconductor material layer, and after theformation of the semiconductor layer, the contact hole exposes a portionof the dielectric layer.

According to one embodiment of the present invention, the method furtherincludes forming an ohmic contact layer on the semiconductor materiallayer after the formation of the semiconductor material layer, andpatterning the ohmic contact layer to expose a portion of thesemiconductor material layer after the formation of the pixel electrode.

The present invention further provides a method for manufacturing apixel structure. The method for manufacturing a pixel structure includesthe following steps. First, a first conductive layer is formed on asubstrate. The first conductive layer is patterned to form a gate byusing a first mask. Next, a dielectric layer is formed over thesubstrate to cover the gate. A semiconductor material layer is formed onthe dielectric layer. The semiconductor material layer is patterned toform a semiconductor layer on the dielectric layer by using the firstmask again. Next, a second conductive layer is formed over thesubstrate. The second conductive layer is patterned to form asource/drain over the substrate by using a second mask. Next, a thirdconductive layer is formed over the substrate. The third conductivelayer is patterned to form a pixel electrode over the substrate by usinga third mask, wherein the pixel electrode is electrically connected tothe drain.

According to one embodiment of the present invention, the step ofpatterning the semiconductor material layer includes the followingprocedures. First, a patterned photo-resist layer is formed on thesemiconductor material layer by using the first mask. The semiconductormaterial layer is patterned to form a semiconductor layer by using thepatterned photo-resist layer as a mask. Then, the patterned photo-resistlayer is removed. Furthermore, the method further includes forming anohmic contact layer on the semiconductor material layer after theformation of the semiconductor material layer, and patterning the ohmiccontact layer by using the patterned photo-resist layer as a mask beforepatterning the semiconductor material layer.

According to one embodiment of the present invention, the step offorming the source/drain further includes patterning the dielectriclayer by using the source/drain as a mask to expose a portion of thesubstrate.

In summary, the method for manufacturing a pixel structure provided bythe present invention uses only four mask process, wherein two masksteps employ the same mask. Thus, not only the fabrication cost iseffectively reduced, but also the fabrication throughput can beeffectively increased. Because the method for manufacturing a pixelstructure requires comparatively less number of mask steps, andtherefore fabrication yield can be effectively increased.

In order to the make aforementioned and other objects, features, andadvantages of the present invention more comprehensible, preferredembodiments accompanied with appended drawings are described in detailbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1G depict cross-sectional views illustrating a method formanufacturing a conventional pixel structure.

FIGS. 2A to 2N depict cross-sectional views illustrating a method formanufacturing a pixel structure according to a first embodiment of thepresent invention.

FIGS. 3A to 3C depict different terminal structures respectively.

FIGS. 4A to 4G depict cross-sectional views illustrating a method formanufacturing a pixel structure according to a second embodiment; and

FIGS. 5A to 5C depict different terminal structures respectively.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIGS. 2A to 2N depict cross-sectional views of a method formanufacturing a pixel structure according to a first embodiment. First,referring to FIGS. 2A to 2D, the method for manufacturing the pixelstructure of this embodiment can be used to manufacture a pixelstructure for a thin film transistor with a bottom gate. Thismanufacturing method includes the following steps. First, a gate 112 isformed on a substrate 10 by using a first mask M1. The substrate 10 is,for example, a glass substrate, a quartz substrate, or any substratewith a suitable material. As shown in FIG. 2A, the method of forming thegate 112 includes, for example, forming a first conductive layer 110 onthe substrate 10 through physical vapor deposition (PVD), or anysuitable methods such as sputtering or evaporation, wherein the firstconductive layer 110 comprises, e.g., Al, Mo, MoN, Ti, TiN, Cr, CrN, orany suitable material. In one embodiment, the first conductive layer 110comprises, for example, TiN/Al/Ti/TiN composite layer, wherein thethickness of Al is, for example, between 500 and 1000 angstroms, and thethicknesses of Ti and TiN are, for example, between 300 and 1000angstroms. Next, a photo-resist layer 120 is coated on the firstconductive layer 110. The photo-resist layer 120 is, for example, anegative photo-resist.

As shown in FIG. 2B, subsequently an exposing process and a developingprocess are carried out using the first mask Ml to form a photo-resistlayer 122. Next, as shown in FIG. 2C, a dry etching or the wet etchingprocess is carried out using the photo-resist layer 122 as a mask toremove a portion of the first conductive layer 110 not covered by thephoto-resist layer 122. Thus, a gate 112 is formed. As shown in FIG. 2D,after the formation of the gate 112, a stripping process is carried outto remove the photo-resist layer 122.

Referring to FIG. 2E, a dielectric layer 130 is then formed over thesubstrate 10 to cover the gate 112. The dielectric layer 130 is formed,for example, through plasma enhanced chemical vapor deposition (PECVD)at a process temperature lower than 300° C., or through any othersuitable method. In addition, the dielectric layer 130 comprises, forexample, SiNx, SiOx, SiOxNy, or any other suitable material, and thethickness of the dielectric layer 140 is, for example, between 1500 and3000 angstroms.

Referring to FIG. 2F, after the formation of the dielectric layer 130, asemiconductor material layer 140 and a second conductive layer 150 aresequentially formed over the dielectric layer 130. In this embodiment,in order to improve the electrical property, an ohmic contact layer L1may be formed on the semiconductor material layer 140 after theformation of the semiconductor material layer 140, however, the presentinvention is not limited to forming the ohmic contact layer L1. Themethod of forming the semiconductor material layer 140 is, for example,achieved through chemical vapor deposition or another suitable method.The semiconductor material layer 140 comprises, for example, anamorphous silicon (α-Si), poly silicon or any other suitable material.The ohmic contact layer L1 may be formed by chemical vapor deposition orany other suitable method. The ohmic contact layer L1 comprises, forexample, an N type doped amorphous silicon or any other suitablematerial. The second conductive layer 150 may be formed vacuumsputtering or any other suitable method. The second conductive layer 150comprises, for example, indium tin oxide (ITO), indium zinc oxide (IZO),or any other suitable material.

Referring to FIGS. 2G to 2I, the second conductive layer 150 is thenpatterned to form a pixel electrode 152 by using a second mask M2. Asshown in FIG. 2G, the pixel electrode 152 may be formed, for example, asfollows. First, a photo-resist layer (not shown) is coated on the secondconductive layer 150. The photo-resist layer is etched using the secondmask M2 to form a patterned photo-resist layer 162. Then, as shown inFIG. 2H, the second conductive layer 150 is etched using the patternedphoto-resist layer 162 as a mask to form a pixel electrode 152. Duringthe formation of the pixel electrode 152, a contact hole H may also beformed for exposing part of the semiconductor material layer 140. Asshown in FIG. 2I, after the formation of the pixel electrode 152, a dryetching process is first carried out for patterning the ohmic contactlayer L1, and then a stripping process is carried out to remove thephoto-resist layer 152. It should be particularly noted that, althoughthe contact hole H and the pixel electrode 152 are formed at the sametime in this embodiment, it is unnecessary for the contact hole H to beformed simultaneously with the pixel electrode 152.

Referring to FIG. 2J, a patterned photo-resist layer 172 is formed overthe substrate 10 by using the first mask M1 again for protecting thesemiconductor material layer 140 above the protect gate 112. Thepatterned photo-resist layer 172 may be formed by the following process.First, a photo-resist layer (not shown) is coated on the semiconductormaterial layer 140 and the pixel electrode 152. Next, the photo-resistlayer is etched using the first mask M1 as a mask to form the patternedphoto-resist layer 172.

Referring to FIGS. 2K and 2L, the semiconductor material layer 140 ispatterned to form a semiconductor layer 142 using the pixel electrode152 and the patterned photo-resist layer 172 as masks. A dry etching ora wet etching process may be carried out to pattern the semiconductormaterial layer 140 to form the semiconductor layer 142 such that aportion of the dielectric layer 130 is exposed by the contact hole H.Next, an etching process is carried out using the pixel electrode 152and the patterned photo-resist layer 172 as masks to pattern thedielectric layer 130 such that a portion of the substrate 10 is exposed.Then, as shown in FIG. 2L, a stripping process is carried out to removethe patterned photo-resist layer 172. It should also be noted that, theetching process for patterning the dielectric layer 130 is an optionalprocess and may not be necessary.

Referring to FIGS. 2M to 2N, a source 182 and a drain 184 are formedover the substrate 10 by using a third mask M3. As shown in FIG. 2M, themethod of forming the source 182 and the drain 184 is illustrated asfollows. First, a third conductive layer 180 is deposited over thesubstrate 10 to cover the semiconductor layer 142, the pixel electrode152 and a portion of the substrate 10. Next, a photo-resist layer (notshown) is coated on the third conductive layer 180. The photo-resistlayer is etched using the third mask M3 as an etching mask to form apatterned photo-resist layer 192. As shown in FIG. 2N, a portion of thethird conductive layer 180 is etched using the patterned photo-resistlayer 192 as a mask and then the patterned photo-resist layer 192 isremoved so that the source 182 and the drain 184 are formed. Here, thethin film transistor TI is formed, with the drain 184 electricallyconnected to the pixel electrode 152. Thus, the fabrication of the pixelstructure 100 is completed.

Accordingly, the method for manufacturing the pixel structure accordingto an embodiment of the present invention, only four mask steps areused, wherein two mask steps of the four mask steps use the same mask.Thus, the fabrication cost of the pixel structure is substantiallyreduced and the fabrication yield is substantially increased. Moreover,the fabrication throughput is substantially increased.

The method for manufacturing the pixel structure of this embodiment mayalso be used for manufacturing terminal structures. FIGS. 3A to 3Cdepict different terminal structures 200, 300, 400 respectively. Theseterminal structures 200, 300, 400 can be used for, for example, a wiringarea of an active element array substrate (not shown) as a bonding pad,an inner short ring, or any other element. Furthermore, the structure ofthe terminal structures 200, 300, 400 may vary depending on the designof the mask. It should be noted that the metal wires 210, 220 and thetransparent wire 230 of the terminal structure 200 are formedsimultaneously along with the formation of the gate 112, the source 182,and the pixel electrode 152 of the pixel structure 100 respectively.Similarly, the metal wire 310 and the transparent wire 320 of theterminal structure 300 are formed simultaneously along with theformation of the gate 112 and the pixel electrode 152 of the pixelstructure 100. The metal wire 410 and the transparent wire 420 of theterminal structure 400 are formed simultaneously along with theformation of the source 152 and the pixel electrode 152 of the pixelstructure 100.

Second Embodiment

FIGS. 4A to 4K depict cross-sectional views of the pixel structure ofaccording to a second embodiment. Referring to FIG. 4A, the method formanufacturing the pixel structure of this embodiment includes thefollowing steps. First, a gate 112 is formed on a substrate 10 by usinga first mask Ml, and a dielectric layer 130 is formed over the substrate10 to cover the gate 112. The first mask M I and the substrate 10 arethe same as that described in the first embodiment; and themanufacturing method, the material, and the thickness of the gate 112and the dielectric layer 130 are the same as those described in thefirst embodiment.

Referring to FIGS. 4B to 4E, a semiconductor layer 512 is then formed onthe dielectric layer 130 by using the first mask Ml again. The method offorming the semiconductor layer 512 includes the following steps. First,as shown in FIG. 4B, first a semiconductor material layer 510 is formedon the dielectric layer 130; and a photo-resist layer (not shown) isformed on the semiconductor material layer 510; and the photo-resistlayer is etched using the first mask M1 as a mask to form a patternedphoto-resist layer 522. Then, as shown in FIG. 4C, an etching process iscarried out to pattern the semiconductor material layer 510 using thepatterned photo-resist layer 522 as a mask to form the semiconductorlayer 512. Subsequently, a stripping process is carried out to removethe patterned photo-resist layer 522. It should be noted that, after thesemiconductor material layer 510 is formed, an ohmic contact layer L2 isformed on the semiconductor material layer 510. Before the semiconductormaterial layer 510 is patterned, the ohmic contact layer L2 is patternedusing the patterned photo-resist layer 522 as a mask.

Referring to FIGS. 4D to 4E, a source 532 and a drain 534 are formedover the substrate by using a second mask M4. As shown in FIG. 4D, themethod of forming the source 532 and the drain 534 is illustrated asfollows. First, a second conductive layer 530 is deposited on thedielectric layer 130 and the semiconductor layer 512; and a photo-resistlayer (not shown) is coated on the second conductive layer 530. Thephoto-resist layer is etched using the second mask M4 as a mask to formthe patterned photo-resist layer 542. Next, as shown in FIG. 4E, anetching process is carried out to remove a portion of the secondconductive layer 530 by using the patterned photo-resist layer 542 as amask to form the source 532 and the drain 534. After the source 532 andthe drain 534 are formed, a stripping process is carried out to removethe patterned photo-resist layer 542. It should be noted that, the stepof forming the source 532 and the drain 534 further includes carryingout the etching process by using the source 532 and the drain 534 as amask to pattern the dielectric layer 130 and expose a portion of thesubstrate 10. It should be noted that, the etching process forpatterning the dielectric layer 130 is optional and may be notessential.

Referring to FIGS. 4F to 4G, a pixel electrode 552 is formed over thesubstrate 10 by using a third mask M5. The pixel electrode 552 iselectrically connected to the drain 534. As shown in FIG. 4F, the methodof forming the pixel electrode 552 is illustrated as follows. First, athird conductive layer 550 is deposited over the substrate 10 to coverthe source 532, the drain 534 and the channel layer 512; and aphoto-resist layer (not shown) is formed on the third conductive layer550. Next, the photo-resist layer is etched using the third mask M5 toform a patterned photo-resist layer 562. Subsequently, as shown in FIG.4G, the etching process is carried out using the patterned photo-resistlayer 562 as a mask to remove a portion of the third conductive layer550 and thereby form the pixel electrode 552. Next, after the pixelelectrode 552 is formed, a stripping process is carried out to removethe patterned photo-resist layer 562. Thus, the fabrication of the pixelstructure 500 is completed.

Thus, the method for manufacturing the pixel structure according to thisembodiment also uses only four mask steps, wherein two mask steps usethe same mask. Therefore, the fabrication throughput is increased, andthe overall fabrication cost is substantially reduced.

The method for manufacturing the pixel structure of this embodiment canalso be used for manufacturing the terminal structures. FIGS. 5A to 5Cdepict different terminal structures 600, 700, 800 respectively. Itshould be noted that, the metal wire 610 and the transparent wire 620 ofthe terminal structure 600 are formed simultaneously along with theformation of the gate 112 and the pixel electrode 552 of the pixelstructure 500 respectively. Similarly, the metal wire 710 and thetransparent wire 720 of the terminal structure 700 are formedsimultaneously along with the formation of the source 532 and the pixelelectrode 552 of the pixel structure 500; and the metal wires 810, 820of the terminal structure 800 are formed simultaneously along with theformation of the gate 112 and the source 552 of the pixel structure 500respectively.

In summary, the method for manufacturing the pixel structure provided bythe present invention has at least the following advantages.

1. The method for manufacturing the pixel structure provided by thepresent invention uses only four mask steps, wherein two mask steps usethe same mask, so that the masking cost may be substantially reduced.

2. The method for manufacturing the pixel structure provided by thepresent invention uses only four mask steps to manufacture the pixelstructure, therefore the fabrication throughput may be increased and theoverall fabrication cost may be reduced.

3. Due to the relatively fewer process steps, the number of defectsoccurring during the fabrication of the pixel structure may bedecreased, thus the fabrication yield may be effectively promoted.

4. The method for manufacturing the pixel structure provided by thepresent invention is compatible with current processes, such that noadditional processes or devices are required.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A method for manufacturing a pixel structure, comprising: forming afirst conductive layer on a substrate; patterning the first conductivelayer using a first mask as an etching mask to form a gate; forming adielectric layer over the substrate to cover the gate; sequentiallyforming a semiconductor material layer and a second conductive layerover the dielectric layer; patterning the second conductive layer usinga second mask as an etching mask to form a pixel electrode; forming apatterned photo-resist layer over the substrate using the first mask asan etching mask, such that the semiconductor material layer above thegate is protected; patterning the semiconductor material layer to form asemiconductor layer using the pixel electrode and the patternedphoto-resist layer as an etching mask; removing the patternedphoto-resist layer; forming a third conductive layer over the substrate;and patterning the third conductive layer to form a source/drain byusing a third mask, wherein the drain is electrically connected to thepixel electrode.
 2. The method for manufacturing the pixel structure asclaimed in claim 1, wherein the step of forming the semiconductor layerincludes patterning the dielectric layer by using the pixel electrodeand the patterned photo-resist layer as an etching mask to expose aportion of the substrate.
 3. The method for manufacturing the pixelstructure as claimed in claim 1, wherein the step of forming the pixelelectrode includes forming a contact hole to expose a portion of thesemiconductor material layer, and after the step of forming thesemiconductor layer, the contact hole is formed to expose a portion ofthe dielectric layer.
 4. The method for manufacturing the pixelstructure as claimed in claim 1, further comprising a step of forming anohmic contact layer on the semiconductor material layer after the stepof forming of the semiconductor material layer, and a step of patterningthe ohmic contact layer to expose a portion of the semiconductormaterial layer after the step of forming the pixel electrode.
 5. Amethod for manufacturing a pixel structure, comprising: forming a firstconductive layer on a substrate; patterning the first conductive layerusing a first mask as an etching mask to form a gate; forming adielectric layer over the substrate to cover the gate; forming asemiconductor material layer on the dielectric layer; patterning thesemiconductor material layer using the first mask as an etching mask toform a semiconductor layer on the dielectric layer; forming a secondconductive layer over the substrate; patterning the second conductivelayer using a second mask as an etching mask to form a source/drain overthe substrate; forming a third conductive layer over the substrate; andpatterning the third conductive layer using a third mask as an etchingmask to form a pixel electrode over the substrate, wherein the pixelelectrode is electrically connected to the drain.
 6. The method formanufacturing the pixel structure as claimed in claim 5, wherein thestep of patterning the semiconductor material layer includes: forming apatterned photo-resist layer on the semiconductor material layer byusing the first mask; patterning the semiconductor material layer usingthe patterned photo-resist layer as an etching mask to form thesemiconductor layer; and removing the patterned photo-resist layer. 7.The method for manufacturing the pixel structure as claimed in claim 6,further comprising a step of forming an ohmic contact layer on thesemiconductor material layer after the step of forming the semiconductormaterial layer, and a step of patterning the ohmic contact layer usingthe patterned photo-resist layer as an etching mask before the step ofpatterning the semiconductor material layer.
 8. The method formanufacturing the pixel structure as claimed in claim 5, wherein thestep of forming the source/drain further includes patterning thedielectric layer using the source/drain as an etching mask to expose aportion of the substrate.